1. Field of the Invention
The present invention relates to a circuit device and a manufacturing method thereof, and more particularly relates to a circuit device which has a multilayer wiring structure including conductive patterns having different thicknesses, and a manufacturing method thereof.
2. Description of the Related Art
With reference to FIGS. 22A and 22B, a description will be given of a configuration of a conventional hybrid integrated circuit device. This technology is described for instance in FIG. 1 in p. 4 in Japanese Patent Application Publication No. Hei 6 (1994)-177295. FIG. 22A is a perspective view of a hybrid integrated circuit device 100, and FIG. 22B is a cross-sectional view along the line X–X′ in FIG. 22A.
The conventional hybrid integrated circuit device 100 has a configuration as described below. The hybrid integrated circuit device 100 includes a rectangular board 106, an insulating layer 107 provided on the surface of the board 106, a conductive pattern 108 formed on the insulating layer 107, a circuit element 104 fixed on the conductive pattern 108, a thin metal wire 105 which electrically connects the circuit element 104 and the conductive pattern 108, and a lead 101 electrically connected to the conductive pattern 108. The hybrid integrated circuit device 100 described above is entirely sealed with a sealing resin 102. As a method for sealing the device with the sealing resin 102, there are injection molding using a thermoplastic resin, and transfer molding using a thermosetting resin.
However, in the hybrid integrated circuit device 100 as described above, it is required to change a film thickness of a conductive pattern between a hybrid integrated circuit board (hereinafter referred to as a board) on which an element of a high current power system is mounted and a board on which an element of a small signal system is mounted.
For example, the film thickness is 100 μm in the power system, and 35 μm in the small signal system. However, if boards are separately prepared and mounted for the power system and the small signal system, costs are increased and miniaturization is difficult to achieve. Ideally, the power system and the small signal system are mounted on one board.
Furthermore, if the power system and the small signal system are mounted on one board by use of a Cu foil of a power system having a thickness of 100 μm, there is a problem that a pattern interval is increased since, of course, the Cu foil is thick. Moreover, although a pattern of the small signal system may be thin, weight is increased because the Cu foil is thick.
On the other hand, if the power system and the small signal system are mounted on one board by use of a Cu foil of a small signal system having a thickness of 35 μm, a minute pattern can be realized but there is a problem that it is impossible to flow a large current since, of course, the Cu foil is thin. Specifically, in the conventional case, the securing of a current capacity (a thick pattern), a thin pattern, and miniaturization are in a trade-off relationship.
Moreover, nowadays, an element such as a high-performance and high-power system LSI is included in a hybrid integrated circuit device. In order to include such an element having a great number of pins, it is required to form a more complex pattern inside the device and to secure high heat release properties. However, in the hybrid integrated circuit device 100 as described above, the conductive pattern 108 is formed of a single-layer wiring. Thus, it is difficult to allow wirings to intersect with each other. In order to allow the conductive patterns 108 to intersect with each other, a configuration using a jumper wire is also conceivable. However, in the case of using the jumper wire, a parasitic inductance may be generated in a portion of the jumper wire. Moreover, in the case where multiple layers of wirings are formed on the surface of a circuit board 16, there is also a problem that heat release properties of the entire device are lowered.
Moreover, in the case where a printed board having multiple layers of wirings is used as the circuit board 16, there is a problem that, since the printed board has poor heat release properties, it is difficult to include elements which generate a large amount of heat. Furthermore, in the case of adopting a ceramic board, there arises a problem that a wiring resistance is increased.